Measuring received signal strength or making other forms of radio link measurements represents a relatively common aspect of on-going operations between nodes in a wireless communication network. In networks based on the Third Generation Partnership Project, “3GPP”, Long Term Evolution, “LTE”, specifications, for example, items of user equipment, “wireless device 30s”, make periodic or triggered measurements on various signals. These measurements support link adaptation for best efforts service—e.g., modulation and coding scheme selections to dynamically tailor transmission data rates or other transmission aspects as a function of radio link quality.
Further, on-going radio link measurements support mobility management, such as where the wireless device 30s report signal quality with respect to various base stations—“eNodeBs” in the LTE nomenclature—in support of dynamically selecting which cells in the network are used to serve the wireless device 30s. Similarly or additionally, radio link measurements support positioning operations, either by the wireless device 30s or by the network. Further, self-organizing network, “SON”, procedures depend on dynamically determining relative radio link qualities, as do operations for Minimization of Drive Time or “MDT”, Closed Subscriber Group or “CSG” cells, etc.
Additional scenarios involving generally recurring radio link measurements include Carrier Aggregation or “CA” service, wherein service to a given wireless device 30 involves simultaneous transmission on more than one carrier. The term Component Carrier or “CC” describes each of the individual carriers used in a CA scenario. CCs may be contiguous in frequency or may be non-contiguous in frequency. When all of the CCs involve the same Radio Access Technology or “RAT”, the CA scenario is referred to as “inter-RAT CA”. The term “inter-RAT CA” applies in scenarios involving more than one RAT—i.e., two or more of the CCs aggregated for service come from different RATs. Common CA scenarios include the use of Distributed Antenna Systems or “DAS”, the use of Remote Radio Heads, “RRHs”, and Coordinated Multi-Point or “CoMP” configurations, which provide service via a coordinated set of cells.
In another LTE-specific example, the network transmits different types of signals at pre-defined times. Synchronization signals—Primary Synchronization Signals or “PSS” and Secondary Synchronization Signals or “SSS”—are sent in subframes one (1) and five (5). Further, Cell Reference Signals or “CRS” are transmitted in every subframe—e.g., at symbol times zero (0), four (4), seven (7) and e11, or a subset thereof in case of special subframes or MBSFN subframes. Similarly, system information—including the Master Information Block or “MIB” and the System Information Block 1 or “SIB1”—is sent in pre-defined subframes. Likewise, Positioning Reference Signals or “PRS” are sent in predefined subframes, e.g., in six consecutive subframes every 160 ms, to facilitate Observed Time Difference of Arrival or “OTDOA” positioning and wireless device 30s are correspondingly requested to perform Received Signal Received Power, “RSRP”, or other such measurements at the appropriate times.
The above measurements and other operating activities presume the availability of the involved signals, at least at the times when measurements are performed. Consequently, interruptions of the involved radio links can cause unreliable behavior, e.g., inaccurate radio signal measurements inadvertently taken during instances of radio link interruption, improper determinations of synchronization or loss of synchronization arising from signal loss during radio link interruption, etc.